1. Field of the Invention
The present invention relates to a video overhead display system. More particularly, the present invention relates to a video overhead display system which can accurately position an object and reverse and magnify an image of the object.
2. Description of the Prior Art
A video overhead display system generally includes a table for holding an object, an image pick-up device for converting an optical image of an object into an electronic image signal, and support means for supporting the image pick-up device. Further, the image pick-up device is usually provided with a zoom lens unit which enlarges the optical image, according to a fixed magnification (typically eight times). A video output device receives the image data from the image pick-up device and displays the video image of the object.
The video output device typically comprises either a video display unit or both a video display unit and a video processor. The video display unit converts the image data received from the image pick-up device and displays the video image. The display unit may, for example comprise a cathode-ray tube, a liquid crystal display, or a flat panel display. If a video processor is included in the output device, the processor stores and re-processes the image data received from the image pick-up device before outputting the image data to the video display unit.
FIG. 14 illustrates a prior art video overhead display system. Referring to FIG. 14, the prior art video display system includes a body 2, an object plate 3, a main pole rotating portion 4, a light box 5, a main pole 6, a head rotating portion 7, a camera head 8, and lamp units 9. An object, such as a film image, is placed on object plate 3, which comprises part of body 2. Main pole 6 comprises two parts which cooperate to allow its length to be adjusted. Main pole 6 connects to main pole rotating portion 4, which, in turn, connects to a middle, raised portion of body 2. Main pole rotating portion 4 allows main pole 6 to be rotated to predetermined angles. Head rotating portion 7 connects at one end to an upper portion of main pole 6, while its other end connects to camera head 8. Camera head 8 picks-up the optical image of the object and is connected to portion 7 such that it can rotate in the vertical plane. Camera head 8 may also include an adapter lens 8a. Lamp units 9 are connected to body 2 at the left and right sides of main pole rotating portion 4.
In the prior art video overhead display system described above, the position of camera head 8 is controlled by adjusting the rotation of main pole rotating portion 4, the length of main pole 6, and the vertical rotation of camera head 8 on head rotating portion 7. Through this adjustment process. the image pick-up device mounted in camera head 8 can capture the optical image of the object.
The system may also includes light box 5, which is optionally placed on top of object plate 3. Light box 5 is used when a transparent object is being viewed by the display system. Further, a control panel 2a is provided on the front of object plate 3 for controlling the image pick-up and lighting functions.
The operation of the above prior art video display system will now be described. An object is placed on object plate 3, and a user selects a magnification value (e.g., 8 times) using control panel 2a. The lens system of camera head 8 focuses and magnifies the image, according to the selected magnification value. As a result, an optical image of the object is formed on the image pick-up device disposed in camera head 8. The image pick-up device converts the optical image into an electronic image signal and outputs image data to a video output device (not shown).
Generally, the image pick-up device comprises a charge coupled device (CCD). The CCD is comprised of a plurality of pixels, and the optical image which forms on each pixel is converted into an electronic image signal. Each electronic image signal is then output in a regular sequence.
When the object is cellular tissue or a microorganism, the display system highly magnifies the optical image using a separate image microscope and lamps. The image microscope generally includes an object lens, which has three predetermined magnifications that may be selected by a user. The optical image that passes through the obiect lens is inverted turned (turned upside-down), and the inverted image is then transmitted to the image pick-up device through an eye lens.
Depending on the object to be displayed (i.e., film documents, etc.), suitable optical lenses are mounted to adapter lens 8a. However, the above video overhead display system has the drawback in that a separate image microscope and lighting device is required whenever the user wants to view a highly magnified image. In addition, if the image microscope is used, then the image may only be magnified using one of the predetermined magnifications of the object lens (typically 3 magnification values). Thus, control of the image magnification is limited, making it difficult to attain the exact degree of magnification desired by a user.
Furthermore, since the prior art video overhead display system does not have an image reversing function, the system is often difficult to use. Namely, when the image microscope is used, it is difficult to adjust the image pickup location and to view the object since its image is inverted.
Finally, since the image pick-up position is adjusted using main pole 6, main pole rotating portion 4, and camera head 8, the image pickup angle is greatly limited. Thus, if the shape of the object is complicated, then it must be continuously re-positioned in order for its image to be picked-up by the pick-up device. As a result, image pick-up of the object becomes difficult.